Looking at building a vivarium - can I keep crabs?

Hi everyone! I saw this awesome video about a vivarium this guy made which mimics a rainforest:


I have loads of experience with tropical tanks and am eager on trying something a bit more challenging and different!

He had a freshwater crab and a whole load of other creatures (most of which seem to be things I can find here in South Africa).

It seems like freshwater crabs are not something we can find for sale here in aquarium shops here in SA. I saw that it appears on the black list, but so do shrimps (which you can find in abundance) and I am not sure how heavily this is policed?

Does anyone have experience in creating this sort of ecosystem and have any suggestions or insights into alternatives or other exotic creatures that I could safely (and happily and ethically etc) keep and add to this ecosystem? It doesn’t seem like this kind of thing is big here in SA, so if anyone can point me in the right direction and/or give me any pointers and advice, I’d greatly appreciate it!